Question: My engine is leaking oil past the valve cover
gaskets. I've tried tightening down the valve cover bolts, but
it doesn't seem to help. What should I do?
Answer: Bite the bullet and buy a new set of valve cover
gaskets. Most cork valve cover gaskets usually cost less than
and are fairly easy to install on many engines. You may
have to disconnect and remove some plumbing or other accessories
to get to the valve covers, but on many engines the job is usually
within the capabilities of a do-it-yourselfer. If the valve covers
are buried or access is difficult, then let a professional replace
the gaskets for you.
Tightening the valve cover bolts or screws will rarely stop
an oil leak because the gasket is usually cracked, crushed or
has lost its natural elasticity. Cork gaskets only last about
four to six years before they age harden, become brittle and start
to leak. Molded silicone rubber gaskets, on the other hand, (which
are used on many late model domestic and import engines) often
last the life of the engine. But molded rubber gaskets are a
lot more expensive than die cut cork gaskets. That's why cork
gaskets have long been used by the vehicle manufacturers.
Some engines do not have gaskets, but instead use a rubbery-glue
called "RTV silicone sealer (the "RTV" stands for
Room Temperature Vulcanizing). If this is the case, you can remove
the valve cover, scrape off all the old RTV, and either apply
a fresh bead of RTV silicone sealer to the valve cover flange
or head mating surface or install a conventional gasket.
CAUTION: Do not let any pieces of rubber or debris fall into
the engine. Also, if you decide to use RTV sealer and your engine
has an oxygen sensor (which almost all 1981 and later engines
do), make sure the RTV sealer is the "low volatile"
variety that is approved for use with oxygen sensors. Some types
of RTV give off silicone vapor that can be sucked through the
crankcase and contaminate the oxygen sensor.
